A conventional electronic component mounting apparatus will be explained referring to FIGS. 9 and 10 which are a schematic view of the apparatus and a flowchart of controlling the same, respectively.
An electronic component feeding means 1 comprises a movable table 2, component feeders 3, and a drive mechanism 4. The component feeders 3 are mounted in a row parallel to each other on the movable table 2 which is driven in the X-axis direction by the drive mechanism 4 including a motor. Each of the component feeders 3 includes a reel 5 for storage of a tape on which a multiplicity of electronic components are carried in a row. As the tape is drawn out to a component feeding position 6, the electronic components are picked up one by one.
An electronic component mounting means 7 comprises a drive mechanism 8, a speed reducer 9, an input shaft 10, an indexing device 11, a rotary body 12, and nozzles 13 (13a to 13d) for picking up electronic components by suction. As power is transmitted from the drive mechanism 8 via the speed reducer 9 to the indexing device 11, a continuous rotating motion of the input shaft 10 is converted to an intermittent rotation of the rotary body 12. The nozzles 13 (13a to 13d) are located at equal intervals about the rotary body 12, each nozzle being separately driven for rotation and vertical movements around and along their respective shafts.
When the component feeding position 6 of the component feeder 3 is defined just below one of the nozzles 13, the nozzle 13 is descended to pick up an electronic component 14 by suction (Step #1). After the nozzle 13 is lifted up, the rotary body 12 rotates to convey the electronic component 14 towards this side in FIG. 9. While being conveyed, the electronic component is examined by an electronic component suction detecting mechanism (not shown) whether it is held by suction or not (Step #2). The nozzle 13 is then positioned just above an imaging means 15 which takes an image of the electronic component 14 held by suction on the nozzle 13. The state of the electronic component 14 being attracted by suction is checked by analyzing the image of the electronic component 14 with a recognition controlling means 16 (Step #3). Based on the analyzed result, the position and angle of the electronic component 14 are corrected (Step #4). The correction is intended for determining the optimum mounting position and angle of the electronic component 14 to a circuit board 17.
The circuit board 17 on which electronic components are mounted is horizontally supported on a board support 18 which is linked to an X-axis drive mechanism 19 and a Y-axis drive mechanism 20 for moving and positioning the circuit board 17 at a desired position in the horizontal plane.
For mounting the electronic component 14 onto the circuit board 17, the circuit board 17 is adjusted to position a mounting location thereon just below the nozzle 13. When the nozzle 13 is descended, it releases and places the electronic component 14 at the mounting location on the circuit board 17 (Step #5). Then, the nozzle 13 is lifted up and returned.
A single electronic component 14 is mounted through carrying out such series of actions. For mounting a plurality of electronic components 14, the series of actions as described above are repeated for each one of the electronic components 14 (Step #6) according to the predetermined data on mounting positions and order.
After a long run of operation for mounting electronic components 14 onto the circuit board 17, the nozzle 13 may be fouled at its tip or damaged inside (e.g. nozzle choking or valve failure), hence failing to perform stable sucking action of the electronic component 14. For example, if the tip of the nozzle 13 attracting the electronic component 14 is fouled, its image taken by the imaging means 15 may appear different from a normal state, causing a recognition error in the recognition controlling means 16 which will fail to calculate for correction. Consequently, the electronic component 14 cannot be correctly mounted. Also, if the nozzle 13 is choked or has a valve failure, it cannot attract the electronic component 14 by suction. These unfavorable states of suction which disturb the mounting operation of the electronic component 14 will be hereinafter referred to as a suction error.
For maintaining a stable action of attracting the electronic component 14, each of the nozzles 13 is monitored at Step #2 whether or not a suction error has occurred. It is then judged if the suction error is repeated on the same nozzle 13 by a given number of times (Step #7). If so, it is judged that the nozzle 13 is defective (Step #8) and it is avoided from use in the following cycle.
This is hereinafter referred to as a faulty nozzle judging function. An operator is at the same time informed that the nozzle has been identified as a defective nozzle.
Upon being informed, the operator stops the operation and views the condition of the nozzle 13 which has been identified as defective. If the nozzle 13 is heavily fouled, the operator takes a proper step such as cleaning the nozzle before restarting the operation.
In such a conventional method implemented in the electronic component mounting apparatus, however, it may happen that the nozzle 13 which works normally is also defined as defective when there is a source of suction error other than the faultiness of the nozzle (for example, when the electronic component 14 has not been properly fed to the component feeding position 6 in the electronic component feeder 1). In that case, the nozzle 13 cannot be used again unless the operator stops the operation and changes the setting of the nozzle from "defective" to "normal". This will produce a downtime of the electronic component mounting apparatus hence decreasing the efficiency of production.
As shown in FIG. 11, when nozzles are actually fouled (with dust or obstacles) during the operation and identified as defective (denoted by the black dots in FIG. 11) by the faulty nozzle judging function, they stay out of use in the following cycles of the production. If a nozzle (denoted by the x marked dot in FIG. 11) is erroneously regarded by the faulty nozzle judging function as defective due to the occurrence of some errors in the electronic component feeder side, it is also kept out of use in the following cycles. Accordingly, while the defective nozzles remain out of use, the production continues with the use of a less number of the nozzles and its efficiency will be declined. Eventually, even if there is the normal nozzles (denoted by the x marked dot in FIG. 11), the number of usable nozzles decreased to null, causing the operation to be stopped.
Also, if the nozzle 13 is judged as defective due to a cause other than the contamination on the nozzle (choking or valve failure), another step is further required to specify the exact cause of faultiness by checking the tip of the nozzle 13. Such an extra step for identifying the source of suction error increases the downtime of the apparatus and decreases the efficiency of production.
As described above, the conventional method for controlling the electronic component mounting apparatus has two problems: the faulty nozzle judging function originally designed for increasing the productivity may interrupt the production; and there may be a substantial loss of time after the operation is stopped upon detecting a defective nozzle.
In view of the foregoing, it is thus an object of the present invention to provide a method of mounting electronic components which can automatically judge the condition of a nozzle which has been identified as defective, and if it is judged that the nozzle is not defective, the nozzle is used in the cycles of operation and when the nozzle is defective, the data on its defective condition is transferred to an operator for implementing efficient and smooth maintenance services to increase the productivity.